What do you think this lens is most useful for and what styles should be avoided when using this lens?

Now I'm even considering selling it and getting 24-70 II, but I might miss the bokeh of 35L.

I shoot indoor portraits with ambient light at whatever f/ is needed to keep iso down. I absolutely love the versatility/availability of going to f/1.4 when needed and would never trade this one in for the 24-70 II. It might as well be glued to the 60D since it rarely comes off, though my wife and I took only our 35L and 5Dii on vacation and had no regrets. With that, I can't think of any "styles" that are outside of the reach of this lens apart from its physical limitations (i.e. fixed at 35mm) I hope that helps, but personally, I think this lens is pretty awesome.

I took some photos of a friend driving his monster truck last summer (2011), and ended up having to use the 35mmL and cropping the images severely. Even wide open and severely cropped, I can print large prints.f/1.4